Production of organic acids

ABSTRACT

A PROCESS IN WHICH A NEO-ACID IS REACTED WITH A COMPOUND CONTAINING ONE OR MORE ISOALKYL GROUPS IN THE PRESENCE OF A STRONG ACID, PREFERABLY SULPHURIC ACID, TO PRODUCE A SECOND NEO-ACID.

United States Patent U.S. Cl. 260-537 R 9 Claims ABSTRACT OF THE DISCLOSURE A process in which a neo-acid is reacted with a compound containing one or more isoalkyl groups in the presence of a strong acid, preferably sulphuric acid, to produce a second neo-acid.

The present invention relates to the production of neoacids.

It is known to produce neo-acids by reaction of an olefin and formic acid in the presence of concentrated sulphuric acid or by reaction of an olefin and carbon monoxide in the presence of boron trifiuoride. By neo-acid is meant a tertiary carboxylic acid, i.e. one in which the a carbon atom is attached to three other carbon atoms. It has now been discovered that neo-acids can be reacted with compounds having one or more tertiary hydrogen atoms when intermolecular rearrangements will occur.

Accordingly the present invention is a process in which a neo-acid is reacted with a compound containing one or more tertiary hydrogen atoms in the presence of strong acid to produce a second neo-acid.

The compound containing one or more tertiary hydrogen atoms can also be a neoacid, in which case the products of reaction will be a di-neo-acid and an isoparaffin. Thus the invention provides a useful method for producing di-neo-acids. Alternatively the compound containing the tertiary hydrogen atoms may be an isoparafiin, in which case the product of reaction will be a second iso-parafiin and a second neo-acid containing the carbon skeleton of the original isoparafiin. Thus the invention provides a method for producing neo-acids which may not be readily prepared by the methods mentioned earlier, from nee-acids which are readily prepared.

Formic acid will suppress the rearrangement reaction. Thus if the neo-acid is made by a route which involves formic acid, the formic acid must be removed before the neo-acid is used.

The neo-acid preferably contains from 5 to 20 carbon atoms. The number of carbon atoms in the compound containing a tertiary hydrogen atom depends on the exact structure of the compound, but compounds containing from 8 to 20 carbon atoms are preferred.

The molar ratio of neo-acid to compound containing tertiary hydrogen atoms is not very critical and ratios in the range 0.1 to 10.0 moles of acid per mole of compound containing tertiary hydrogen may be used. It is preferred to use an excess of the compound containing tertiary hydrogen.

The invention is particularly useful for the production of di-neo-acids, either by reaction of two mono-neo-acids which contain tertiary hydrogen atoms or by reaction of a mono-neo-acid with a di-isoparafiin. When the dineo-acid is produced from a mono-acid, the mono-neoacid must have a tertiary hydrogen atom attached to a carbon atom separated from the or carbon atoms of the acid by at least two, preferably at least four carbon atoms. Preferably the mono-acid contains from 9 to 20 carbon atoms. The di-neo-acid may be produced from a single mono-neo-acid or a mixture of mono-neo-acids in which one of the mono-neo-acids has the structure described above.

When the di-neo-acid is prepared by reaction of a mono-neoacid and an isoparafiin the isoparaffin should be a di-isoparaflin which the tertiary hydrogen atoms are attached to carbon atoms which are separated by at least two, preferably at least four carbon atoms. The di-isoparaffin preferably contains 8 to 19 carbon atoms. The mono-neo-acid used should not contain any tertiary hydrogen atoms attached to a carbon atom which is separated by 2 or more carbon atoms from the or carbon atom of the acid. If it does, reaction between two molecules of mono-neo-acid will occur much more quickly than reaction between mono-neo-acid and di-isoparaifin, and the di-isoparaffin will remain unchanged.

Whenever it is desired to react a mono-neo-acid with a compound containing a tertiary hydrogen atom which is not a neo-acid, the mono-acid should not contain a tertiary hydrogen atom attached to a carbon atom separated by two or more carbon atoms from the a carbon atoms. If it does the neo-acid will react more quickly with itself than the other compound.

The reaction is carried out in the presence of strong acid. The acid may be a Bronsted acid preferably with a pK value greater than 2 such as hydrofluoric, perchloric, chlorosulphonic, fiuorosulphonic or sulphuric acid. Nitric acid should not be used as oxidation reaction may occur rather than the desired rearrangement. Lewis acids may also be used. Preferred Lewis acids are pentafiuoro antimonate in admixture with hydrogen fluoride, boron trifiuoride and phosphoric acid or boron trifluoride and hydrofluoric acid.

The preferred acid is sulphuric acid whose concentration is not less than 90% w./w., preferably not less than 97% w./w. Not less than 1 mole of sulphuric acid should be used per mole of neo-acid. The preferred amount is 5 to 10 moles of sulphuric acid per mole of neo-acid. With mixtures which react only slowly it may be preferred to use up to 20 moles of sulphuric acid, and it is believed that up to 40 moles is adequate in all cases.

The reaction temperature should not be greater than C. as oxidative side reactions may occur, and preferably not greater than 60 C. It is particularly preferred to operate at ambient temperature, below 40 C.

The reaction time required is a function of the skeletal structure of the reagents, the reaction temperature and the catalyst used, but it should exceed one second. Reactiont times of the order of one hour and more may conveniently be used.

The compound produced by the invention may find use for example in the manufacture of esters, plasticisers and polymers.

EXAMPLE 1 45.42 g. of 97% w./w. deuterium sulphate was added under stirring at 23 C. to 8.8 g. of neo-undecanoic acids which contained 74.5% w./w. of 2:2:7-trimethyl octanoic acid. Samples were withdrawn from the stirred mixture at selected intervals, quenched in 4 volumes of water and the precipitated 2:2:727-tetramethyl suberic acid (M.P. l80-4 C.) was washed with water and cyclohexane, dried and assayed. The results of this experiment are given in Table 1.

1 Based on 2:2:7-trimethy1octanoie acid used.

3 EXAMPLE 2 49 g. of 99% w./W. sulphuric acid was added at 22 C. to 9.3 g. of neo-undecanoic acids which contained 83% w./w. of 2:5-dimethyl-2-ethyl heptanoic acid. Sam- 4 EXAMPLE 5 Reaction of an aliphatic mono-neo-acid which contains an isoalkyl group with an isoparaflin which contains two isoalkyl groups ples were withdrawn from the stirred mixture at selected 5 intervals and the 2:2:7z7-tetramethyl suberic acid (M.P. mmethyl butyr-lc acidand dlmethyl 1877 5 C) was isolated as described in Example 1 octane was mlxed with 99% H2504 (49 The res'ults given in Table 2 g.) at ca. 20 and was then allowed to stand for 27 days. The mixture was poured into four volumes of water and TABLE 2 the precipitated 2:227:7-tetramethyl suberic acid (0.150 Percent 10 g.) was separated by filtration. The regenerated neo-acids g ggifii (5.18 g.) were separated from the catalyst rafiinate and Dried nwacid to found to contain a small amount of 2:2:7-trimethyl oc- Du at n zg n di-nwacid tanoic acid. This experiment demonstrated that one or both tertiary hydrogens present in the 2:7-dimethyl octane 3% g: 15 may be replaced by carboxyl groups. 168 0.243 36.6 EXAMPLE 6 Basedon 2:5-d1methyl-2-etl1ylheptan c used- Reaction of an aliphatic mono-neo-acid which does not EXAMPLE 3 contain an isoalkyl group with an isoparaifin which Productions of di-neo-acids from polyisomeric 20 contams two lsoalkyl groups mixtures of mono-neo-acids 2:2-dimethyl pentanoic acid (3.045 g.) and 2:7-dimeth- The neo-acid was added to the sulphuric acid catalyst Y1 octane were mlxed with 99% 2 4 at ambient temperature under stirring. Stirring was main- (49 at and then allowed to Stand for 11 tained for ca. 6 h. and then the mixture was allowed to dayS' The,react1n Processed by the Procedure stand for several days before dilution with an equal weight desFnbefl Example ylelded 2:2:7i74etramethyl f of Water. The regenerated nee-acids were partitioned with benc acid Q 5- and a Small amount of 232174 cyclohexane (3 volumes), separated from solvent and methyl octanolc acld' isoparafiins by extraction with excess aqueous sodium hy- EXAMPLE 7 droxide solution and regenerated again with excess hydrochloric acid. The regenerated neo-acids liquid phase The effect vanatlon catalystlneo'amd molar was separated, water washed and dried. Increase in acidity ratio and reacuon temperature of the nee-acid product was a measure of the di-neo-acid These experiments were carried out by the procedure content. The results are given in Table 3. given in Example 5 and the results are given below.

TABLE 3 Extrapelated, Reaction Percent W./W. acid percent Reagents, molar ratio assay of product content of Run Temp., Duration di-neo-acids number Mono-neo-acid used Neo-acids H2804 degrees (d.) Initial Final inproduct 1 C13 acids ex propylene tetramer- 1 20 ca. 22 7 99. 2 140. 3 73 2 do 1 1e. 7 ca. 22 7 99.8 146. 2 so 3..-. C13 acids ex buteue trimer 1 20 ca. 22 9 100 117. 5 37 C m acids on propylene trimer 1 10 ca. 22 7 100 103.3 a 12 1 This experiment was carried out on 0.85 mole scale based on nee-acids used and the remainder With 25 or 60 mm. of neo-acids.

I This nee-acid was commercially produced by Enjay 8 Includes 2% yield of 2:2:616-tetramethyl pimelic acid (MCP: 1(i7168.5 0).

EXAMPLE 4 Reaction of an aliphatic mono-neo-acid with more than one isoalkyl group in the chain Neo-tridecanoic acid (5.35 g.; mainly 2:6-dimethyl-2- isobutyl heptanoic acid) was mixed with 99% W./w. H 80 (49 g.) at ambient temperature and then stood for 18 days. The neo-acids product, separated from neutral substances by the procedure described in Example 3, had an increased acid assay (6.5% W./|W. increase based on 111. wt. 214) which corresponded to ca. 16% w./w. content of C di-neo-acids.

Reagents, molar ratio 2-ethyl-2z5- Reaction Time for drmethyl heptatemp., half reaction Run number noic acid H2804 C.) (d.)

1 When the reaction temperature was increased to C. oxidation side reactions predominated and the yield of di-neo-acids acre depressed.

5 No reaction after 35 days.

EXAMPLE 9 one day. The reaction product yielded a solid di-neo-acid d (M.P. 114-175 C., 36% yield) and this consisted of Pro Ion of a 1 ac1d w1t Lewls acld catalyst 2-ethyl-2.7.7-tr1methylsuberic acid and 2.2.8.8-tetramethyl- 2.2.7-tr1methyl octanoic acid (2.96 g., 0.016 m.) and 1 1,; id,

a 121:0.75 molar mixture of BF :H PO :H O (58 g.) EXAMPLE 4 were mixed and allowed to stand at ca. 20 C. for 10 days. 5 The reaction mixture was then treated with an equal Rearrangement of mono-neo-acid other than 11,0:- volume of water and cyclohexane and the precipitated dimethylalkanoic acids 2.2.7.7-tetramethyl suberic acid (M.P. 185 C., wt. 0.0074 yield) was isolated by filtration A mixture (25 mmol of 2-methyl-2-butyloctano1c and 2-ethyl-2-propyloctanoic acids was mixed with 99% w./w. EXAMPLE 10 sulphuric acid 500 mmol) at 20 c. for 7 days. A 41% 2 2 4 4- 1 Valerie acid 79 5 2 7- conversion of the mixture of mon-o-neo-acids to di-neodimethyl octane (H g, 005 m) and 99% 50 49 aclds was obtained. The purified di-neo-acid (M.P. 115 0.5 m.) were mixed together and then allowed to stand Shown to be z-z-9-9-tetl'amethylsebacic acidat ca 20 C. for 35 days. The reaction product was then I clalm: treated with 4 volumes of water and the precipitated A Process for the Production of di-neo-acids, 2.2.7.7-tetramethyl suben'c acid (M.P. 186 0., wt, 0.065 prlsmg contacting at a temperature of not more than g.=0.00027 m.==l% yield) was isolated by filtration, about 80 C. a mono-neo-acid as the only reactant with a strong acid selected from the group consisting of 90- EXAMPLE 11 100% wt./wt. sulphuric acid and Lewis acids to produce l-carboxy-1.2-diiosobutyl cyclohexane (3 g., 12.5 mm.) a di-neo-acid, said mono-neo-acid containing 9 to 20 carand 99% H 80 (24.5 g., 0.25 m.) were mixed and stood bon atoms and having a tertiary hydrogen atom attached for 3 days at ambient temperatures. The reaction mixture to the carbon atom separated by at least two carbon was then treated with 4 volumes of water and the organic atoms from the a-carbon atom thereof. phase separated by partition with cyclohexane (2X 10 2. A process according to claim 1 in which the strong ml.). The neo-acid products were chemically separated acid is 90100% wt./wt. sulphuric acid and between 1 from neutral reaction products. The isolated neo-acid and 40 moles of said 90-100% wtjwt. sulphuric acid are product (1.33 g.) contained of a di-acid of the used per mole of mono-neo-acid. same g-l/c elution time as 2.2.11.11-tctramethyl dodecan- 3. A process according to claim 1 in which the tertiary dioic acid and this result was confirmed by acid assay. 30 hydrogen atom is attached to a carbon atom separated EXAMPLE 12 The effect of conformation of alieylic mono-neo-acid on the yield of dineo'acid Molar ratio used Per nt Run Duration yield of No. H 804 Nee-acid (d.) Mono-nee acid used di-neo-acids 1 21 1 19 COOH c0011 0 (2.2.2) and (3.2.1)-bicyclo octane-l-carboxylate 2 2O 1' 3 All 141 OOOH OOOH l-earboxy-l.2-diisobutyl-cyelohexane 3 2O 1 2 H H 6 E OOH COOH -carboxy-2.2-dimethyl-(4.3.1) and (4.2.2) bicycledecane.

1 A neutral product, identified as a mixture of 1.2-diisobutylcyclohexane and 1.i-diisopropyleyclooctane, was obtained from this reaction.

i A solid di-neo-acid (M.P. 179.5-181.5 C.) was isolated from this reaction which was apparently l-carboxy- 1(4 carboxy4'methyl pentyl) cyelohexane (Mixed M1. and infra-red spectroscopic analysis).

EXAMPLE 13 by at least four carbon atoms from the a-carbon atom of p the mono-neo-acid. Preparation of di-neo-acids other th th Q 4. A process for the production of a di-neo-acid which t tr th l lk di i id comprises contacting an open-chain mono-neo-acid containing 9 to 20 carbon atoms and having a tertiary hydro- 6-ethyl-2.2-dimethyloctanoic acid (5 mmol) was mixed 7 gen atom attached to a carbon atom separated from the with 99% w./w. sulphuric acid (100 mmol) at 20 C. for a-carbon atom thereof by at least two carbon atoms as the only reactant with 90-100% wt./wt. sulphuric acid at a temperature of not more than 60 C. and a reaction time of at least 1 second.

5. The process according to claim 1, wherein the strong acid is 90l00% wt./wt. sulphuric acid.

6. The process according to claim 1, wherein the strong acid is a Lewis acid.

7. The process according to claim 6, wherein the Lewis acid is pentafiuoro antimonate in admixture with hydrogen fluoride, boron trifiuoride and phosphoric acid, or boron trifluoride and hydrofluoric acid.

. 8. The process according to claim 4, wherein the tertiary hydrogen atom is attached to a carbon atom separated by at least four carbon atoms from the a-carbon atom of the mono-neo-acid.

9. The process according to claim 4, wherein between 1 and 40 moles of said 90-100% wt./wt. sulphuric acid are used per mole of mono-neo-acid.

8 References Cited UNITED STATES PATENTS 3,515,737 6/1970 Yeomans 260413 FOREIGN PATENTS 913,041 12/ 1962 Great Britain 260-533 OTHER REFERENCES Hine, Physical Organic Chemistry, 2nd ed., pp. 311- Meinwald et al., J.A.C.S. 82, 483 (1960).

LORRAINE A. WEINBERGER, Primary Examiner 5 R. GERSTL, Assistant Examiner us. 01. X.R. 260-514 R, 533 R 

